Build a relationship graph and run BFS to answer queries

Problem: Build a relationship graph and answer reachability queries with BFS You are given undirected relationships between entities and multiple queries. For each query (s, t), determine whether there exists a path from s to t following relationship edges. Input (stdin) First line: two integers n m — number of relationships and number of queries. Next n lines: two strings u v — an undirected edge between u and v. Next m lines: two strings s t — one query. Output (stdout) For each query output one line: YES if t is reachable from s NO otherwise Constraints 1 <= n, m <= 2e5 Identifiers are alphanumeric/underscore strings, length 1..30 Must handle large input sizes Example Input: 4 3 A B B C D E C A A E D E Output: YES NO YES Example Input 4 3 A B B C D E C A A E D E Output YES NO YES